Science: Magnetic Havoc

At least 171 times in the past 76 million years, the earth's magnetic
field has mysteriously faded in strength and then returned to normal
with the North and South poles reversed. Scientists have long suspected
that these reversals may somehow be linked with such old biological
puzzles as the sudden disappearance of the dinosaurs some 65 million
years ago. Now investigators from Columbia University's Lamont-Doherty
Geological Observatory have added new evidence to the old speculations.
They report that six species of Radiolariatiny marine
animalssuddenly became extinct during or shortly after switches in
the earth's magnetic poles.